This invention relates to the art of bag making, and is more particularly concerned with bags having reclosable zippers of the extruded complementary rib and groove type.
Heretofore, numerous and varied bag structures of this type have been proposed and some have achieved substantial commercial success.
For example, U.S. Pat. No. Re. 28,969 discloses a bag structure in which the bag body web and the zipper profiles are extruded in one piece and the bag has pull flanges which project outwardly relative to the zipper.
In U.S. Pat. No. 4,430,070 the zipper is fusibly attached to the bag wall web spaced inwardly from the pull flanges which project outwardly from the zipper.
Both of these examples require that the bag body web and the zipper profiles be fusibly compatible, that is that one can be fused onto the other by some sort of heat sealing means.
On the other hand, U.S. Pat. No. 4,341,575 is representative of disclosures wherein zipper strips are attached to the bag wall web by adhesive means, and which would permit fusibly incompatible materials to be used. However, it will be noted that this disclosure requires fairly critical parameters in the adhesive attachment to avoid separation of the elements. Adhesive attachment generally involves some messiness due to the necessary manner of application of the adhesive to the elements.
Fused attachment of the elements is generally preferred, but presents a problem where the zipper strips and the bag body web are fusibly incompatible. For example, while polypropylene may be fused to polypropylene, and polyethylene may be fused to polyethylene, there is great difficulty encountered in any attempt to fuse or heat seal polyethylene to polypropylene. In bags, while polyethylene is widely used, both for the bag body web material and also for the profiled zipper strips, for one thing because of the ease of extruding such material, the polyethylene material does not afford the imperviousness that is frequently desired where fluid barrier is required. Sometimes, also, other web material incompatible to fusing together with polyethylene may be desired, while the profiled zipper strips should be extruded from polyethylene.
It is to the problem of making bags from fusibly incompatible bag body web material and extruded plastic profile zipper strips that the present invention is directed.
In the prior art, there has been the suggestion in U.S. Pat. No. 2,791,807 that separable fasteners with stringers be constructed of extruded plastic profile fasteners attached to fabric stringer tapes so that the plastic strips may be attached by sewing the fabric tape stringers to the articles to which the fastener strips are desired to be secured. The structure in that patented disclosure does not lend itself to embodiment in bags, and more particularily bags made from plastic wall web material, and provided with pull flanges at their open tops.